N-(tert-Butoxycarbonyl)-N'-[4-(pyridin-2-yl)phenylmethylidene]hydrazine in the present invention is useful as a synthetic intermediate for compound (A) represented by the following formula ##STR2## which is an anti-HIV drug, and the method for the production of the pharmaceutical compound (A) via the intermediate is described in, for example, WO97/40029.
WO97/40029 discloses a production method comprising reacting 4-(pyridin-2-yl)benzaldehyde with tert-butyl carbazate [tBuOC(.dbd.O)NHNH.sub.2 wherein tBu is tert-butyl] to give N-(tert-butoxycarbonyl)-N'-[4-(pyridin-2-yl)phenyhmethylidene]hydrazine, therefor 4-(pyridin-2-yl)benzaldehyde is important as an intermediate for a pharmaceutical product.
The method for the production of 4-(pyridin-2-yl)benzaldehyde includes a method disclosed in, for example, Japanese Patent Unexamined Publication No. 95157/1991 and WO97/40029, wherein Grignard reagent prepared from 4-bromobenzaldehyde dimethyl acetal and 2-bromopyridine are reacted using [1,3-bis(diphenylphosphino)propane] nickel(II) chloride as a catalyst. With regard to the above-mentioned production method, 4-bromobenzaldehyde dimethyl acetal and 2-bromopyridine, which are reaction reagents, are relatively expensive, and [1,3-bis(diphenylphosphino)propane] nickel(II) chloride, which is a catalyst, is extremely expensive and industrially hard to obtain. Thus, it is desired to have a method of producing 4-(pyridin-2-yl)benzaldehyde at a lower cost.
Inasmuch as tert-butyl carbazate used as the reagent in the aforementioned hydrazine derivative production method (WO97/40029) is expensive, a production method for producing N-(tert-butoxycarbonyl)-N'-[4-(pyridin-2-yl)phenylmethylidene]hydrazine industrially and economically has been awaited.
It is therefore an object of the present invention is to provide an economical method for the production of 4-(pyridin-2-yl)benzaldehyde, to provide an intermediate for producing 4-(pyridin-2-yl)benzaldehyde, and a method for the production of this intermediate. Another object of the present invention is to provide a method for producing N-(tert-butoxycarbonyl)-N'-[4-(pyridin-2-yl)phenylmethylidene]hydrazine economically and easily, as well as an intermediate (4-(pyridin-2-yl)benzaldehyde hydrazone) useful for producing this hydrazine derivative and a production method of this intermediate compound.